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CHICAGO — Chicago is the nation’s most congested choke-point for train traffic in the country, but a $4 billion dollar infrastructure project aims to separate freight and commuter lines, with the aim to speed commutes and commerce.

Over a century, the rail lines became a tangled mess, with busy commuter trains competing with freight trains for rail track space throughout the city. It leads to massive traffic jams, bottlenecks and frustration for Chicago commuters and national rail companies alike.

Chicago commuters collectively waste thousands of hours each weekday at street-level rail crossings. Chicago resident Bobby Mitchell said he wastes 20 minutes of his day sitting in traffic and counting train cars. “I learned something about these trains,” Mitchell said. “You got to go find a way just to go around them sometimes.”

About a quarter of all rail traffic in the United States rumbles through the city. That includes 500 freight trains each day carrying everything from fuel to food, cars to cattle.

Freight trains come to a complete standstill during the morning and evening rush hours as preference is given to commuter trains through what’s known as the “Chicago protocol.”

“Commuters are given priority and that costs us roughly two hours a day — time off the clock that we can’t use to move trains,” Tim Coffey of the Belt Railway Company said.

As transit officials from Washington, D.C., and Chicago toured some of the city’s most congested train tracks Wednesday, Mayor Rahm Emanuel says he’s made fixing the problem a top priority in his administration.

“Chicago is a spaghetti bowl of both commuter rail and cargo rail, and this whole investment strategy is untangling that spaghetti bowl,” he said. “Everybody gets in everybody else’s business, and if you separate them, the cargo or freight moves much more efficiently. The economy becomes much more efficient.”

Backed by public and private entities, the $4 billion Chicago Region Environmental and Transportation Efficiency Program (CREATE) funds 70 projects around Chicago designed to speed things up, doing everything from removing tracks from street level by creating overpasses and underpasses, to separating freight and commuter trains.

Emanuel and the program’s backers hope this will also keep hundreds of thousands of jobs in the region, pump the economy with money and save the most important resource of all: time.

“All of this is connected, and Chicago’s history is written chapter and verse by transportation. … If we don’t invest in it, we atrophy,” Emanuel said.